Experiments are planned to explore the neural and humoral interactions between the pineal organ and the diencephalon, and to determine how this interaction impinges on pituitary function. The initial part of the project involves electrophoretic application of wheat germ azglutinin-horseradish peroxidase (WGA-HRP) to the pineal, followed by racing of HRP-positive cells within thediencephalon. In the next series of experiments, a cocktail consisting of tritium labeled leucine, lysine and proline will be applied by electrophoresis to the habenular nuclei and to the suprachiasmatic nuclei (SCN). The injections will be followed by autoradiographic tracing of labelled nerve fibers and terminals in the pineal. lastly, th enfluence of the pineal on hypothalamic control of pituitary hormone secretion will be studied in conscious, freely-moving intact, pineal sectioned and SCN lesioned animals. The secretion patterns of luteinizing hormone (LH) and prolactin will be related to the secretion pattern of one known pineal secretory product, melatonin. The exploration of the anatomical connections between the pineal and the diencephalon will help establish the yet unknown factors controlling the pineal. Combined with the hormone data, information should be provided so as to further elucidate the physiological role of the pineal in modifying pituitary hormone secretions.